How the Sun Works

Daven Hiskey 2
This is a fantastic educational video by Henry Reich from MinutePhysics (with Bonus Sun Facts below written by me). MinutePhysics also sells a few t-shirts here, if you’re interested.
If you’ve got an educational video you’d like featured on Today I Found Out, you can contact me here.

Bonus Sun Facts:

  • The energy required to stop the Earth orbiting the Sun is about 2.6478 × 10^33 joules or 7.3551 × 10^29 watt hours or 6.3285*10^17 megatons of TNT.  For reference, the largest nuclear explosion ever detonated (the Tsar Bomba by the Soviet Union) “only” produced 50 megatons of TNT worth of energy.  So it would take about 12,657,000,000,000,000 of those nuclear bombs detonated at the correct location to stop the Earth from orbiting the Sun.
  • The Sun is white, not yellow.  For you graphics people or web developers out there, the exact color of the sun is #fff5f2.  The reason the Sun looks yellow to us on Earth is that our atmosphere scatters light from the Sun; so the apparent color of the Sun changes.  This same scattering effect is why the sky looks blue in the day time instead of black, like at night.
  • Once regarded by astronomers as a small and relatively insignificant star, the Sun is now known to be brighter than about 85% of the stars in the Milky Way.
  • Light travels from the Sun to the Earth in about 8 minutes and 19 seconds. While it only takes 8 minutes and 19 seconds for the light from the surface of the Sun to reach us, it actually takes about 10,000-170,000 years for a photon to travel from the core of the Sun to the surface.
  • The Sun does not have enough mass to go supernova and explode.  However, in about 5 billion years it will enter a red giant phase steadily expanding until it consumes the Earth.  But fear not, the Earth will already be dead in about 1 billion years due to the fact that the Sun becomes about 10% brighter every billion years; so in 1 billion years the Earth’s surface temperature will be such that no liquid water will be able to exist unprotected on the surface of the Earth.
  • It takes approximately 225 million Earth years for our solar system to make one trip around the Milky Way.
  • Each second about four million metric tons of matter is converted to energy within the Sun’s core.  This gives the Sun a lifetime as a main sequence star of about 10 billion years with about 5 billion years to go.
  • The “surface” temperature of the Sun is about 5780 K, which is equivalent to just under 10,000 F and 5,500 C. The temperature at the core is much hotter, close to 14 million Celsius degrees or 25 million degrees Fahrenheit.
  • This nuclear fusion is self-regulating. If the Sun’s diameter gets smaller while maintaining the same mass, the pressure at the core increases creating more nuclear fusion which in turn causes it to expand.  If it expands maintaining the same mass, the pressure lessens in the core resulting in less nuclear fusion going on.  So a natural equilibrium has resulted in this process with the Sun, though there are stars that can be observed going through a process of massive expansion and contraction at very steady rates.
  • At the core of the Sun, nuclear fusion power produced is estimated at about 276.5 watts/m^3.  Interestingly this power production is more equivalent to a reptile’s metabolic energy production than what we would think like a nuclear bomb.
  • The amount of energy per (W/m^2) deposited on the surface of the Earth from the Sun is about 1368 W/m^2.
  • The Sun is about 150 million km or about 93 million miles from the Earth; this is by definition one astronomical unit (1 AU).
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2 Comments »

  1. georgia December 10, 2013 at 9:31 am - Reply

    So glad I’ll be dead before all the water runs out, boy was that a smack in the face! its a scary thought to think of.

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